KaeYoss said:It isn't killing the party off to change a little fact the characters aren't supposed to know, anyway.
Unless they have extensive knowledge about dragons (and this one in particular, which seems to be a special one), the characters don't know that dragons have only Dex 10 and can't get Rombat Reflexes.
But they might very well know (especially if they've done any research about dragons) that dragons, especially the older and larger ones, are not very agile or maneuverable. Hell, experienced characters could probably deduce this just from watching the way the dragon moves.